This invention relates to an air handling system for a building and, in particular, such a system employing one or more induction units adapted to mix two air flows.
A variety of air handling systems for both large and small buildings are already known in the air handling industry. Air handling systems both for residential and commercial buildings can include the use of a central heating system that includes a fan unit capable of blowing heated air through air ducts that deliver the air to the various rooms of the building. When this system is used in conjunction with a central air conditioner, it is also capable of providing cool air to the various rooms through the air ducts. A relatively large fan is generally required for a large commercial or industrial building. Air silencers can be installed on both the inlet side and outlet side of these large fans to reduce the noise levels created by the operation of such fans.
It is also known to provide so called induction units that employ the venturi effect to mix together both return air from a building and primary air. The two air flows are mixed in a mixing chamber located adjacent an elongate air plenum with a primary air inlet at one end. Tapered nozzles extend into the mixing chamber and are connected to a wall of the air plenum. The return air from serviced space enters the mixing chamber which is flanked by the induction unit's coils on one side and five sides of the enclosure of the unit. There is an opening on the sixth side of the enclosure for entry of the return air. These units can typically be mounted on a wall of a room with the air plenum section located near the floor and the air outlet located at the top of the unit. Such induction units have at least several advantages including the ability to operate at very low noise levels since they do not employ any fans or similar air circulating devices. They can also be used in conjunction with both high pressure as well as low pressure air duct systems and they provide for a reasonably efficient mixing of the primary air and the return air.
Systems for delivering treated air to a room through an outlet located in the ceiling are already known. For example, U.S. Pat. No. 4,672,887 which issued Jun. 16, 1987 to Fred Sproul Sr. describes an air delivery system located above a horizontal ceiling in a dwelling. The air duct system delivers treated air to a valance/diffuser air system that can be located adjacent one wall of the dwelling. The conditioned or treated air is forced into the air delivery system by a blower of a conditioning unit such as a forced air furnace. At the wall the air is initially distributed lengthwise along an elongate horizontal chamber and then distributed through apertures in a downwardly direction. However, this known system does not use air induction units for mixing return air and primary air. In this known system the return air system is located beneath the floor of the dwelling.
More recent U.S. Pat. No. 5,577,958 issued to Mitsubishi Denki Kabushiki Kaisha in November, 1996 describes a ceiling-embedded cassette type air conditioner located above a decorative grate or panel through which return air can pass. A blower is located centrally in this air conditioner and it forces the return air through two or more heat exchangers located on the perimeter of the blower. The conditioned air is returned to the room through two or more outlets located at the ceiling level. Air directing plates can be positioned in the air outlets and these can direct the outflowing air to flow into the room at an angle to the horizontal. This known air conditioning system does not employ any induction unit that relies on the venturi effect and, because it employs a blower, it will be quite noisy when it is operating.
It is an object of the present invention to provide an air handling system for a building which employs at least two induction units and which is capable of mixing return air and primary air efficiently and quietly.
It is a further object of the present invention to provide an air handling apparatus for a building that includes two induction units, which apparatus can be manufactured and installed at a reasonable cost and can be operated and maintained at a low cost.